Shells are comprised of that which traps you within your illusionary being. They are behaviors, the attitudes behind them and the energy of their origin. As a friend put it, they are the bars through which you see the world. What you see of that other side isn't a reflection of divine reality even though that is exactly what you are looking at. Shells are things that reflect the less than true self and all the energy you put in to your own suffering. Shells are what traps you in hell.
It can be supposed that the shells are made up of bad things. I suppose that is true. When you see your shells you will not be surprised by the bad things you have done. After all, even though you deny them to others, you know. Deep down you know. You may be surprised by what is not there or at least relatively minor. What will surprise you are the things you thought were right, okay or no big deal.
I asked you, dear reader, to consider that well.